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Re: [ietf-dkim] RFC4871bis - whether to drop -- k: Key type

2009-06-04 01:58:54
On 6/3/09 12:16 AM, J.D. Falk wrote:
Jon Callas wrote:

   
Okay. I misunderstood. If it's a DNS-level list of all possible
algorithms, it has very limited use, and can go.
     
+1

   

It's not a list.  Dave got it wrong.  Please look at RFC 4871:

    k=  Key type (plain-text; OPTIONAL, default is "rsa").  Signers and
        verifiers MUST support the "rsa" key type.  The "rsa" key type
        indicates that an ASN.1 DER-encoded [ITU.X660.1997] RSAPublicKey
        [RFC3447] (see Sections 3.1 and A.1.1) is being used in the "p="
        tag.  (Note: the "p=" tag further encodes the value using the
        base64 algorithm.)

        ABNF:

        key-k-tag        = %x76 [FWS] "=" [FWS] key-k-tag-type
        key-k-tag-type   = "rsa" / x-key-k-tag-type
        x-key-k-tag-type = hyphenated-word   ; for future extension


The basic question is simply this: is it sufficient to list the key 
algorithm in the header?  I don't see a plausible attack, so I'm okay 
with that.  But let's at least have the debate based on facts.

Eliot
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